Dissolve espresso in 8 tablespoons of boiling water and allow to cool. Mix with liqueur. Stir quark, mascarpone and vanilla sugar until smooth
Line a square flat form (approx. 8 x 13 cm) with half of the lady fingers. Sprinkle with 4-6 tablespoons of espresso mixture. Spread half of the mascarpone cream on top and smooth it down. Place the remaining lady fingers on top and sprinkle with the remaining espresso mixture. Spread the remaining mascarpone cream on top
Cover the Tiramisu and chill for about 4 hours. Dust with cocoa before serving